Kevlar clutch/Motor Miester

Rick Cabell · 03-08-2002, 08:56 AM

After all the stories about MM,I decided to cash in on a $350 credit that I had with them. I needed a clutch for my 74 euro 2.7 carrera,so that's what I ordered. They suggested that I go with the kevlar disc. Before I said OK, I put up a post on this type of clutch and recieved a favorable responce. MM explained that the pressure plate and TOB would be locally rebuilt,not sachs. I was a little hesitant,but went with it. It arrived today and I was quite pleased. The quality in workmanship seemed to be fine. My question involves the kevlar clutch. A stock disc seems to have not that much contact surface for the amount of stress that it has to handle. The kevlar disc has only about 50% of the contact patch compared to a stock one. Also the lining is not very thick. Kevlar is suppose to be extremly durable and last twicw as long as stock. How can the kevlar disc perform with so little contact material? Ther emust be someone out there with full knowledge of these discs, if so please enlighten me. Thanks

BKOMAR · BKOMAR's Garage

My car has a Kevlar clutch disc...from MM actually. I have had no problem with the clutch and the grip/ bite feels fine. The engine/ clutch has only about 11000 miles so I can't comment on the longevity of the part. Brian

Zeke · 03-08-2002, 02:18 PM

I'm probably gonna get in trouble here for chiming in my .02. But, IMHO, the spring rate is constant, whether distributed on a full circle disc, or smaller patches. In other words, you will have more pounds per sq. in. on the smaller pads giving the same bite as more contact at less #PSI. Hence, the Kevlar material to take the load.

It seems like I had better offer a disclaimer here, because I can already feel that a someone is going to jump all over me about this because I am NOT a Clutch Engineer.

kstar · 03-08-2002, 02:38 PM

I think the kevlar cluth as described above is a puck type racing clutch.

I have one from MM as well that had about 80% of life left in it after about 7,000 miles - I never do "burn-out" type launches.

After getting used to the "all or nothing" type engagement, I can live with the clutch on the street and have never noticed slippage.

Something that I have learned about California law is that there is no legal definition of what "rebuilt" means, except as it relates to transmissions - not sure if a clutch qualifies as transmission in this regard.

I do know that Motor Meister has found great protection under the lack of legal definition of "rebuilds" of motors under California law. One can simply disassemble a motor then put it back together and call it "rebuilt".

Good luck with your kevlar clutch!

Regards,

Kurt

Rick Cabell · 03-08-2002, 06:32 PM

Kurt,
Are you saying that this will be a all or nothing clutch? MM says that the engagement would be as smooth as stock. Not taking their word as gospel truth, I put up a post a couple weeks ago and the two that responded said engagement was smooth. This disc is not the 3 puck type racing type like I have seen in the magazines. The kevlar is distributed evenly around the circumfrance,there just isn't 100% coverage like a stock disc.

DonNewton · DonNewton's Garage

I have one of MM's Kevlar clutches in my 2.7 racer, and it (the clutch) has very smooth, even engagement. Much smoother than my SC, as a matter of fact. You don't have an ON/OFF clutch here. Install it and enjoy!

masraum · 09:16 PM

To answer part of your question concerning the physics of the thing, the frictional force is equal to the coefficient of friction multiplied by the force applied by the pressure plate. Surface area never comes into play.

If you weigh 200lbs and are wearing sneakers with a coefficient of friction of .5 then the force that it would take to get you to slide sideways would be 100lbs regardless of what size shoe you wear.

If you look through any catalogs containing performance clutches you'll notice the more "high performance" the clutch disc the smaller the friction surfaces. I'm guessing the main reason for that is to lower the rotational weight. While in a passenger car long life (more friction material to wear away) is more important than low rotational inertial and weight savings, but that is just my assumption.

Here's a good example of the difference that I am talking about. The clutches on the left are lowest performance and get more performance (race only) as you move to the right.

Zeke · 03-08-2002, 09:37 PM

Steve, isn't that what I was saying? To use your sneaker example, the force is the same regardless of shoe size, but the amount of weight per sq. in. is less with a big shoe. I think I'm missing something here. You're saying that the shoes would wear at the same rate and at the same temp? (conditions, i.e. clutch spring rate being equal, of course).

kstar · 11:38 PM

Hi Rick:

First, I am not sure what kind of clutch you got. I did get a "rebuilt" kevlar cultch that was of the "puck" variety. From your initial description, it sounded to me like you got a puck style clutch.

From your further description, perhaps it is not a puck clutch.

With my puck clutch it is either engaged or not engaged, no in-between. I was able to adjust to this clutch as it was in my daily driver; but when my father would take my car for a run it was entertaining for me to see him lurch forward like a 16 year old learning to drive a "stick".

I guess I am just a bit wary of anything that MM says after some experience trying to resolve some MM "problems" with the counsel of the B.A.R.

I think the California law definitions of "rebuilt" regarding transmissions may have forced MM to offer acceptable transmissions and transmission products.

I do feel strongly that MM does exploit, IMO, the lack of a definition of "rebuilt" under California law as it relates to motors.

Anyone contemplating motor work at Motor Meister owes it to themsleves to contact me at: kurt@starnes.com

Best to you Rick with your clutch and all of the very lucky folks who have solid MM motors!

Regards,

Kurt

masraum · 03-09-2002, 12:22 AM

Zeke, wasn't disputing you just offering more corroborating info, another angle to view it from. I am going to assume again, and think that again I'll be in agreement with you. I believe you are correct that since the force is applied to a smaller area more heat will be created. I'm guessing that like race brakes that don't work until a certain higher than normal temp the high perf clutch will be the same and not have optimal friction until heated up. Again, I think that's more or less in agreement with what you've said.

Rick Cabell · 03-09-2002, 03:24 AM

Masraum...... Thanks for the explaination. My disc looks most like the 2nd from the left,more like a street type.
I highly doubt that MM is rebuilding these in house. The tools neeeded to do the disc,PP,and TOB,are more that your typical shop. The quality and workmanship leave nothing to be desired.
One more thing........ The way to visualy check a clutch disc is to see how close the lining is worn to the rivits. On the kevlar,there is very little distance before you are in rivitland! I hope this wears as well as claimed. Probably be a couple weeks before I install it. I will post my opinion as to the smooth action. Thanks to all......

Zeke · 03-09-2002, 07:57 AM

No Steve, I didn't take it as a dispute. I just wanted to understand fully the postulation offered. I'm sorry, I have a bad reputation for digging way too deep for details. Comes from being a sceptic and not accepting every thing that is said. Particularly in racing.

So the agreement is that the multi pad disc should perform similarly to the full disc, abeit at slightly higher temps during heavy use. Hence the Kevlar. And the three "puck" disc is fior racing as it is a PITA on the street. Right guys?

Early_S_Man · 03-09-2002, 10:39 AM

Guys,

Unless you are buying a carbon/ceramic/sintered metal racing disk, you can't buy a clutch disk any longer that DOESN'T have Kevlar in the friction material! Since asbestos was outlawed, practically All brake linings and clutch disks have Kevlar in the 'mix' of the friction material!

The fact that MM used Kevlar in the description of its' rebuilt clutch disk is absolutely MEANINGLESS!

I have two new Sachs replacement disks for a 915 application, and both have Kevlar in the friction material, but the appearances are completely different! The older disk friction material is flat, without radial grooves, and mostly 'greenish' in appearance, with a few very tiny specs of brass in the lining material. The latest disk from the Sachs Power Kit has radial grooves, a much higher percentage metal flakes content, and darker green and black material between the metallic content.